A display of the kind known to the prior art is disclosed in U.S. Pat. No. 3,834,792.
A rotating cell using a liquid crystal only has uniformly high contrast over the entire area, plus a uniform response characteristic, if its liquid crystal layer is rotated at all points through exactly 90.degree. by the interfaces. It is true that by oblique vapor deposition on the carrier plates, it is possible, to produce surfaces having a high, reproducible orientating power, but it has not previously been possible also to produce a regular liquid crystal structure, which rotating cells need, over the larger areas needed for many applications. This is due primarily to the fact that vapor deposition normally has to be performed from point-like sources. Because of the very geometry of such a deposition arrangement, a layer grows on a substrate which has an oblique vapor deposition angle relative to the source in a manner which varies in magnitude from point to point, and, more especially, varies in direction.
If, as is usual, the two carrier plates used in a display system are assembled together to form a display system so that these plates are rotated through 90.degree. in relation to one another, then virtually at every point on the screen there are areas in the respective vapor deposited layers on these plates which are located opposite one other and which have dissimilar structural deviations. This circumstance then leads to an angle of rotation varying from 90.degree., or even, as in the case of a direction of rotation which is not unambiguously preferred, to orientation disturbances with consequent local incursions into the contrast pattern.
Uniform orientation can be achieved not only by oblique vapor deposition, but also by rubbing the carrier plates with a suitable cloth. This last indicated kind of mechanical surface treatment, however, even if it is carried out most carefully, inherently does not yield reproducible and truly uniform orientations. In relation to the kinds of orientation techniques nowadays being used, this technique in receding steadily into the past.